In recent years, digital still cameras and digital video cameras (hereinafter referred to as digital cameras) with high image quality have seen rapid growth in use. Digital cameras are also, in parallel with this, advancing in compactness and light weight, and compact digital cameras with high image quality have come to be incorporated into cellular telephone handsets and the like. Image pickup apparatuses, a typical form of which is a digital camera, include a lens optical system, which forms an image, and imaging elements, which photoelectric convert light formed as an image so as to output electrical signals. The imaging elements used are electronic devices such as CMOS (complementary metal oxide semiconductor) sensors or CCD (charge-coupled device) sensors or the like. These imaging elements photoelectric convert the distribution of light amount of the image that is formed on the image plane, so as to record it as the image plane image. In order to remove aberrations, lens optical systems are often made up of several aspherical lenses. In the case of incorporating a zoom function, a drive mechanism (actuator) is required to change the distance between a plurality of lens and the imaging elements.
In response to the demand for image pickup apparatuses with higher image quality and more sophisticated functionality, imaging elements have increased in numbers of pixels and higher definition, and image-forming optical systems are advancing in providing lower aberration and improved definition. This has been accompanied by the image pickup apparatus increasing in size, leading to the problem of difficulty in achieving compactness and thinness. With respect to such problem, proposals have been made to adopt a compound-eye structure in the lens optical system, and to use an image pickup apparatus constituted by a plurality of imaging elements and lens optical systems. For example, an imaging lens apparatus has been proposed having a constitution that includes a solid lens array disposed in a planar manner, a liquid-crystal array, and an imaging element (for example, refer to Patent Document 1). This imaging lens apparatus, as shown in FIG. 19, has a lens system that has a lens array 2001 and a variable focal length liquid-crystal lens array 2002 with the same number of lenses, an imaging element 2003, an arithmetic unit 2004, and a liquid-crystal drive unit 2005.
The imaging element 2003 images the optical image formed via this lens system.
The arithmetic unit 2004 image processes the plurality of images obtained from the imaging element 2003 so as to reconstitute the overall image.
The liquid-crystal drive unit 2005 detects focus information from the arithmetic unit 2004, so as to drive the liquid-crystal lens array 2002.
By adopting this constitution, a compact thin imaging lens apparatus with a shortened focal length can be implemented.
A thin-type color camera that has a sub-pixel resolution by combining four sub-cameras constituted by an imaging lens, a color filter, and a detector array has also been proposed (for example, refer to Patent Document 2). This thin-type color camera 200, as shown in FIG. 20A and FIG. 20B, is constituted by a lens 220, a color filter 250, and a detector array 240. The lens 220 has four lenses 220a to 220d. The color filter 250 has four color filters 250a to 250d. The color filter 250, as shown in FIG. 20B is constituted by the filter 250a, which passes red light (R), the filters 250b and 250c, which pass green light (G), and the filter 250d, which passes blue light (B). The detector array 240 images an image of red light, green light, and blue light. With this constitution, it is possible to obtain a full-color image by combining, with red and blue, a synthesized high-resolution image formed from two images of green light, with respect to which the human visual system has a high sensitivity.
In the case of synthesizing a high-resolution image from a plurality of images photographed with this plurality of cameras, it is necessary to synthesize by searching for corresponding points taken from the same region in each of the images. However, because of the occurrence of regions that can be photographed from one of the cameras but that cannot be photographed in what is called an occlusion, being hidden from the other camera behind an object, there are cases in which corresponding points cannot be obtained. There is the problem that, this occlusion region, because of erroneous searching for corresponding points, leads to a deterioration in image quality in the high-definition synthesized image. A known apparatus to solve this type of problem is a multocular imaging apparatus in which, in processing to synthesize a high-definition image from a template image and a reference image, in a region in which it is not possible to obtain pairs of corresponding points, the corresponding point of the template image is used as the synthesized image generated data, and the corresponding point in the reference image is not used as the synthesized image generated data (refer to, for example, Patent Document 3). This multocular imaging apparatus, in synthesizing a high-definition image from two images, of a left imaging system and a right imaging system, has an occlusion region determining unit that determines whether or not an occlusion region exists in which corresponding points cannot be obtained. Patent Document 3 discloses processing in which one of the images is not used as the synthesized image data in the occlusion region. By this constitution, it is said, it is possible to omit the processing procedure in a region in which an occlusion occurs, and also possible to suppress the deterioration of the image quality caused by error handling.